淹水条件下水稻对土壤砷转化的影响OA北大核心CSTPCD

The mobility and bioavailability of arsenic(As)significantly increases in soils under flooded conditions,which facilitates its uptake by rice.However,the effects of As transformation on paddy soils during flooding remain poorly understood.In this study,low-arsenic(15.5 mg·kg-1)and high-arsenic(52.1 mg·kg-1)paddy soils were selected for soil incubation experiments with and without rice plants under flooded conditions.Soil pore water and rhizosphere soil samples were collected on days 7,14,28,42,and 56 during the flooded incubation period and various parts of the rice plants were sampled on day 110 at maturity.Dynamic changes in different arsenic species,soil arsenic fractions,ferrous ions,and molecular components of dissolved organic matter in soils were analyzed to elucidate the mechanism of rice in arsenic transformation in flooded soils.Compared to the treatment without rice,the treatment with rice showed lower proportions of available arsenic and amorphous iron-aluminum oxide-bound arsenic fractions in soils,but higher humic acid-bound and fulvic acid-bound arsenic fractions during the flooded period.The presence of rice decreased the concentrations of dissolved Fe(Ⅱ)in pore water from 43.6-51.3 mg·L-1 to 11.9-19.4 mg·L-1,and increased the concentrations of adsorbed Fe(Ⅱ)on soils from 1.14-1.21 g·kg-1 to 3.73-4.28 g·kg-1 on day 28.Three-dimensional fluorescence spectroscopy analysis showed that the presence of rice significantly increased the fluorescence intensities of fulvic-like,humic-like,tyrosine-like,and tryptophan-like substances in the soil dissolved organic matter.In addition,these organic fractions were significantly positively correlated with the organic matter-bound arsenic fraction in soils(p≤0.05,p≤0.01),but significantly negatively correlated with the available arsenic fraction in soils(p≤0.01 or p≤0.001).Rice grown in high-arsenic soil had straighthead disease,which might be associated with its higher abundance of CHOS and protein/lipid compounds(16.4％and 12.0％,respectively)than in low-arsenic soil(12.8％and 6.62％),as revealed by Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR-MS)analysis.These results indicate that rice cultivation can increase dissolved organic matter in the soil and form more organic matter-bound arsenic fractions,leading to a decrease in available arsenic in the soil,likely via rhizosphere response and root uptake.The finding that rice promotes As immobilization by regulating soil organic matter under flooded conditions provides new insights into the environmental effects of crops on As behavior in soils.